nichanderson

My Feedback: (4)

Are there instances when fuselages have been created from a carbon fiber and honeycomb structure?

We're looking for the lightest weight parts, relatively regardless of cost and man power hours. We're concerned with strength but not overly concerned. More so weight.
Or what would be the lightest composite technique out there? Any ideas ?

Thanks,

Nick Anderson

Mel Francis

A full-size aircraft that I can think of, that uses this construction, was the Rutan Voyager, which went around the world, non-stop. I know this, because I was at their hangar during the pre-flight press conference, and they had a box of small, cut-up samples of exactly that laminate.

I'm glad you mentioned that cost is not a factor, since panels involving a honeycomb layer are quite an involved process, compared to basic bagged laminates.

You'll be working with tacky pre-preg materials and ovens to make this all work in one bagging session,

unless you want to go to the trouble of curing a wet-lam skin layer first,
then removing the bag and gluing the honeycomb in place with another bag,
then removing the bag and beveling the honeycomb edges down to the skin lams,
then completing your final lams over the honeycomb, with a final bagging....whew!

Perhaps a call to the Rutan offices might yield you some info that could be helpful.

nichanderson

My Feedback: (4)

We're from Cal Poly Pomona, about 50 miles from Mojave, so a phone call or actual visit may be in order!
We're competing in the AIAAs Design, Build Fly contest. http://s89264194.onlinehome.us/about/about.php
We are heavily rewarded in this contest for designing an aircraft that is lightweight.

We have little practical knowledge about R/C planes in general, but a boat load of theory and technical knowledge (aerodynamics, control systems, finite materials classes etc.. )
I have a fair amount of experience in composites from building rockets, but that all relates to the process of creating round airframe tubes. (and not complex curved fuselages) We're basing that we can create a fuselage off this idea.
http://www.jcrocket.com/nike-asp.shtml Half way down the page

Current plan as of now is to build a foam blank of the fuselage, make a fiberglass mold of that. Then we will either use Mylar or a mold release, apply a layer of wet carbon, honeycomb (or whatever core material we end up using) by dropping pre cut- pre fit pieces into place, and then another layer of wetted out carbon. We could get access to an autoclave, but suspect we will just end up vacuum bagging it.

Thanks,

Nick Anderson
Aerospace Engineering Major
Cal Poly Pomona
http://s89264194.onlinehome.us/index.php

Mel Francis

Very interesting project. I checked some of your links and wish I was eligible to compete too.

But consider -that your current proposed method does not hold the skin lamination down as flat as if it were bagged separately. A fair amount of excess resin will wick up into your cell area, and the exterior surface will need to be filled later, to address surface voids that were not fully pressed down.

The honecomb material is very springy and will drive you crazy, as it continues to pull up from the base laminate in contoured areas, sometimes pulling that up too.

Add to that, the resin in the final lams will wick down into the cells, and your resulting laminate will be quite a bit heavier than you first intended.

If you have the time, expend the effort to do the laminations in separate steps, and the resulting laminate will be as light as a pre-preg aero-space laminated part.

nichanderson

My Feedback: (4)

Alright, thanks for the info. I can see where the springiness of the honeycomb could be a major problem, along with the epoxy wicking into the honeycomb pores. (Weight = bad)

I don't quite get what you mean by " beveling the honeycomb edges down to the skin lams " ?

With the time and manpower we have available I think this would be well within our grasp. (doing multiple baggings)

Edit: I see that scaled uses this method now. "Scaled elected to use its proven sandwich panel structural arrangement with carbon fiber/epoxy skins and PVC foam cores, virtually identical to a manned aircraft." Any ideas on PVC foam cores. Would this be the flexible type of foam, or hard "blue foam" cut to shape ?

Thanks

Nick

Mel Francis

Consider that at several places on your fuse parts, you might want the exterior laminations to be bonded to the inner, final laminations, to form a finished edge, with no raw honeycomb material exposed.

The technique for this is to sand a beveled edge (about a 35 -45 degree angle) along the honeycomb edge, without cutting through your skin lams, of course. Then you laminate your inner cloth over the entire surface, and the resulting edge has the total thickness of the cloths you used, minus the honeycomb thickness, which is now completely sandwiched and ends at the base of the beveled slope just before that edge.

MJFinegan

My Feedback: (2)

If finances permit, you may consider checking out a flex-core honeycomb. The stuff can accomodate moderate curves both simple and compound. This honeycomb is available in metallic and non-metallic material.

MarkNovack

My Feedback: (3)

Nick,
I cannot tell you how it is done but there is a little shop in the Netherlands making fuselages from honeycomb laminates. I do not believe he is using CF as the outer laminate (I do know that the inside laminate is fiberglass) although we do make CF/honeycomb laminates in our shop for small parts. I am quite sure he is vacuum bagging his mold halves to keep all in place. The end result is an incredibly stiff structure with extemely light weight. The drawback is that it is quite fragile to impacts, but the owners of these airplanes are very careful not to bang them around.

There is also a fellow in Germany making very large models (50-55% scale) from fully vacuum bagged honeycomb laminates and they are also a work of art.

I am not sure that the price is worth the effort, but for those for whom money is not an issue and they want something exotic, that it is. Actually, the guy in the Netherlands seems to be doing them quite affordably.

Mark

dian

Hi, I recomend you to see at www.r-g.de/servise/downloads handook in PDF on english.
Dian

Darrinc

My Feedback: (5)

I could give you a hand. Forget everything you know. I'm in Mojave.

Diablo-RCU

My Feedback: (1)

I would suggest that your group try to gain some practical knowledge with basic model planes. You could do this in parallel with your effort to build the composite masterpiece, but you might be better served by starting with the basics. Your project is very likely to fail because of the simplest problems that are typical for nearly every modeler getting started in R/C. An experienced and successful modeler would be a major asset to your team. Someone that knows which side of the fuselage to put the switch for the receiver.....etc.

davidfee

My personal opinion is that the switch should go on the top of the model so it's equally accessible to lefties and righties, doesn't matter which direction the runway points, won't be in the way for handlaunches, won't be switched off by a rough landing, etc. No joke. I put my switches in the top surface of the fuselage, just behind the wing.

poiboy808

I am looking for a suitable material like a carbon-fiber honey comb material for a 1" flat bottom base for a blimp. When a blimp is filled with heluim, the envelope takes on a "spherical" shape. Custom balloon makers use programs to develop patterns and seam weld them together to obtain the desired shape (animals, objects etc.)  I have already spoken with several custom balloon companies and the flat bottom for an airfoil shape is not possible.............yet.  I feel if I can get some sort of very strong yet lightweight material to use I will be able to hold the bottom of the blimp flat.  I am open to all suggestions

daven

My Feedback: (1)

thanks for bumping this 8 year old thread, that link to the rocket page was pretty cool.

Sorry for not answering your question though, I have no idea.

k_jitsu

Have a look to http://www.uav-technologies.com